Process for preparing 1,4-benzodiazepin-2-ones

ABSTRACT

The process for preparing benzodiazepin-2-one derivatives of the formula   WHEREIN R1 is hydrogen or lower alkyl, and rings A and B are either unsubstituted or substituted by one or more groups of nitro, trifluoromethyl, halogen, alkyl and alkoxy groups, which comprises subjecting a 2-amino- Alpha phenylbenzylideneaminoacetal derivative to ring-closure, hydrolyzing the resultant product to obtain the 2hydroxybenzodiazepine derivative, and subjecting such derivative to oxidation to yield the benzodiazepin-2-one derivative. Also provided are novel 1-alkyl-2-hydroxybenzodiazepine derivatives of the formula   WHEREIN R&#39;&#39;1 is lower alkyl and rings A and B may be either unsubstituted or substituted as defined above, such derivatives being useful as intermediates in the above process and also as tranquilizing agents.

United States Patent Meguro et al.

451 Sept. 19, 1972 1 PROCESS FOR PREPARING 1,4- BENZODIAZEPlN-2-ONES Inventors: Kanji Meguro, Nishinomiya; Hiroyuki Tawada, Kyoto; Yutaka Kuwada, Ashiya, l-lyogo; Tor-u Masuda, Nishinomiya, Hyogo, all of Japan Assignee: Takeda Chemical Industries, Ltd.,

Osaka, Japan 22 Filed: Sept. 3,1969

21 Appl. No.: 855,042

[30] Foreign Application Priority Data Sept. 3, 1968 Japan ..43/63323 Sept. 3, 1968 Japan ..43/63324 [52] US. Cl. ..260l239.3 D, 260/239 BD, 260/566 R,

424/244 [51] Int. Cl. ..C07d 53/06 [58] Field of Search ..260/239.3 D, 239 BD [56] References Cited UNITED STATES PATENTS 3,558,603 l/l97l Yamamoto et al..260/239.3 D

Primary Examiner-Henry R. Jiles Assistant Examiner-Robert T. Bond Attorney-Wenderoth, Lind & Ponack [5 7] ABSTRACT The process for preparing benzodiazepin-Z-one derivatives of the formula wherein R, is lower alkyl and rings A and B may be either unsubstituted or substituted as defined above, such derivatives being useful as intermediates in the above process and also as tranquilizing agents.

2 Claims, No Drawings PROCESS FOR PREPARING 1,4-BENZODIAZEPIN- 2-ONES This invention relates to a novel and industrially advantageous process for producing benzodiazepin-Z-one derivatives of the general formula wherein R, is hydrogen or lower alkyl, and the respective benzene rings A and B may have one or more substituents selected from the groups consisting of nitro, trifluoromethyl, halogen, alkyl and alkoxy. The present invention also relates to novel l-alkyl-Z-hydroxybenzodiazepine derivatives of the general formula (III) wherein R, has the same meaning as defined above and R is lower alkyl and the respective benzene rings A and B may have the same substituent(s) as defined above, to a ring-closure reaction, whereby 2-alkyoxybenzodiazepine derivatives of the general formula wherein R, is as defined above, are provided and finally subjecting the 2-hydroxybenzodiazepine derivatives (V) to oxidation to yield the object benzodiazepin-Z- one derivatives (l).

Referring to the above general formulas, the lower alkyl represented by R, and R, is exemplified by methyl, ethyl, propyl, isopropyhbutyl, sec-butyl, tertbutyl, amyl, hexyl, cyclopentyl or'cyclohexyl. Among these, methyl and ethyl are the most desirable. The respective benzene rings A and B may have one or more of the same or different substituents which are exemplified by nitro, triiluoromethyl, halogen (chlorine, bromine, fluorine and iodine), alkyl (e.g., lower alkyl such as methyl, ethyl, propyl, isopropyl, butyl and secbutyl) and alkoxy (e.g., lower alkoxy such as methoxy, ethoxy, propoxy and butoxy) groups. As the lower alkyl represented by R, those groups having up to six carbon atoms are preferable, which are exemplified by methyl, ethyl, propyl, butyl, pentyl and hexyl groups.

The Z-amino-a-phenylbenzylideneaminoacetal derivatives (III) which are the starting compounds for the process of the present invention can be prepared almost quantitatively, for example, by allowing compounds of the general formula mm, A l

C=NR

wherein R, is as defined above and R is, for example, hydrogen, alkyl or hydroxyalkyl, to react with an aminoacetal of the formula wherein R is as defined above.

According to the first step of the process of the present invention, Z-amino-a-phenylbenzylideneaminoacetal derivatives (III) are subjected to a acid). The amount of acid to be employed is generally about 5 moles to about moles per mole of the 2- amino-a-phenylbenzylideneaminoacetal derivatives (Ill).

The solvent utilized for the ring-closure reaction is exemplified by alcohols such as methanol and ethanol. The ring-closure reaction is generally carried out with heating around the boiling point of the solvent but the reaction may proceed even at room temperature.

The resultant 2-alkoxybenzodiazepine derivative (IV) is then hydrolyzed. The hydrolysis readily proceeds by treating the 2-alkoxybenzodiazepine derivatives (IV) with water.

Generally, the 2-alkoxybenzodiazepine derivatives (IV) are directly subjected to the hydrolysis without isolation, i.e., by adding water to the reaction mixture of the previous step.

The resultant 2-hydroxybenzodiazepine derivatives (V) may be isolated in the form of acid addition salts (e.g., hydrochloride or sulfate). However, the reaction mixture itself may be directly subjected to the subsequent oxidation step without separation of the compound (V).

According to the final step of the present invention, the 2-hydroxybenzodiaepine derivatives (V) are sub jected to oxidation, wherebythe hydroxyl group at the 2-position is oxidized to an oxo group.

The oxidation is generally conducted by a per se known method which has been conventionally used for converting a secondary alcohol into the corresponding carbonyl group.

The oxidation is preferably carried out, for example, by the use of an oxidizing agent such as chromium trioxide, dichromate salts, etc. in the presence of a solvent such as glacial acetic acid, aqueous acetic acid, pyridine, aqueous pyridine, etc.

When the oxidation is carried out in an aqueous solvent such as aqueous acetic acid, the 2-alkoxybenzodiazepine derivatives (IV) can be converted directly to the benzodiazepin-Z-one derivatives (I) through simultaneous hydrolysis and oxidation.

The oxidation is preferably conducted at room temperature or below.

The oxidizing agent is utilized in an amount of at least one equivalent and preferably in an amount of from about one to about two equivalents for each one equivalent of the 2-hydroxybenzodiazepine derivatives (V).

Thus produced benzodiazepin-Z-one derivatives (I) may be isolated in the form of free bases or suitable acid salts (e.g., hydrochloride, sulfate, acetate, etc.) by per se conventional means, for example, by extracting the resulting reaction mixture with a suitable solvent, followed by concentration of the extract. The l-alkyl-2 hydroxybenzodiazepine derivatives (11), which are produced as intermediates in the present process, are novel compounds and in themselves show sedative, taming, muscle relaxant and anticonvulsant effects and therefore are useful as tranquillizing, muscle relaxant and anti-convulsant agents, etc.

The novel l-alkyl-2-hydroxybenzodizaepine derivatives (II) and their acid salts, e.g., the hydrochloride salt, are administered orally or parenterally per se, or in a suitable formsuch as powder, granule, tablet or injectable solutions admixed with pharmaceutically acceptable carrier or adjuvant. The dosage of the l-alkyl- 2-hydroxybenzodiazepine derivatives (ll) or their acid salts to be administered varies with the respective compounds, severity of the disease, etc., and generally falls within a range of from about 1 to about 30 milligrams for oral administration, and from about 0.5 to about 10 milligrams for parenteral administration per day for an adult human.

For a further detailed explanation of the present invention, the following Examples and References are given, wherein the term part(s) means weight part(s)" unless otherwise provided, and the relation between part(s) and part(s) by volume corresponds to that between gram(s) and milliliter(s).

References for the preparation of 2-amino-a-phenylbenzylideneaminoacetal derivatives, the starting material for the process of the present invention, are as follows:

REFERENCE 1 A solution of l 1 parts of 2-arnino-5-chloro-a-phenylbenzylideneaminoethanol, 16 parts of aminoacetaldehyde diethylacetal and 9.4 parts of 2- methylimidazole hydrochloride in 200 parts by volume of ethanol is refluxed for 4 hours, followed by distillation of the solvent. Water is added to the residue and the precipitated crystals are recrystallized from aqueous ethanol to give 2-amino-5-chloro-a-phenylbenzylideneaminoacetaldehyde diethylacetal as colorless pillars. Melting point: 103 to 104 C.

Elementary analysis; Calculated for c n cm o, C 65.79, H 6.68, N

8.08 Found C 65.65, H 6.68, N 8.15

REFERENCE 2 A solution of 11 parts of 2-amino-5-nitro-a-phenylbenzylideneaminoethanol, 16 parts of aminoacetaldehyde diethylacetal and 9.4 parts of 2- methylimidazole hydrochloride in 200 parts by volume of ethanol is refluxed for 3 hours, followed by distillation of the solvent under reduced pressure. The residue is washed with ethanol to yield 2-amino-5-nitro-aphenylbenzylideneaminoacetaldehyde diethylacetal as yellow crystals. Melting point: 157 to 161 C. Recrystallization from ethanol affords yellow prisms melting at 161 to 164 C.

Elementary analysis:

Calculated for C H N O C 63.85, H 6.48, N 11.76

Found C 63.77, H 6.44, N 11.62

REFERENCE 3 A solution of 5.6 parts of 2-methylamino-5chloro-aphenylbenzylideneaminoethanol, 7.8 parts of aminoacetaldehyde diethylacetal and 4.8 parts of 2- methylimidazole hydrochloride in parts by volume of ethanol is refluxed for 4 hours, followed by distillation of the solvent. The oily residue is extracted with ethyl acetate, washed with water and dried over sodium sulfate, followed by distillation of the solvent, whereby 2-methylamino-5-chloro-a-phenylbenzylideneaminoacetaldehyde diethylacetal is produced as yellow crystals.

For identification, a small amount of the crystals is recrystallized from ethanol to give pale yellow needles melting at 62 to 635 C.

Elementary analysis:

Calculated for C H ClN O C 66.56, H 6.98, N

7.76 Found C 66.55, H 6.93, N 7.74

EXAMPLE 1 A solution of 1 part of 2-amino-5-chloro-a-phenylbenzylideneaminoacetaldehyde diethylacetal in 20 parts by volume of ethanol containing percent hydrogen chloride is heated at 50 C. for 10 minutes, followed by concentration of the solution below 40 C. under reduced pressure. The reddish residue is dissolved in a mixture of 10 parts by volume of acetone and 2 parts of volume of water. The solution is left standing for a while, whereby 7-chloro-2hydroxy-5 phenyl-2,3-dihydrol l-l-l ,4-benzodiazepine hydrochloride is obtained as yellow crystals. Melting point: 125 C. (decomposition).

Elementary analysis: Calculated for C l-l ClN o-l-lCl'l-l O C 55.06, H

4.93, N 8.56 Found C 55.10, H 4.65, N 8.95

EXAMPLE 2 A solution of 1.2 parts of 7-chloro-2-hydroxy-5- phenyl-2,3-dihydrol H-l ,4-benzodiazepine hydrochloride prepared in the Example 1 in 6 parts by volume of pyridine is added dropwise with stirring and ice-cooling to a mixture of 0.8 part of chromium trioxide and 5 parts by volume of pyridine. The mixture is left standing at room temperature for 2 hours. Water is added and the mixture is extracted with ethyl acetate. The ethyl acetate layer is washed with water and concentrated under reduced pressure. The residue is recrystallized from acetone to give 7-chloro-5-phenyll,3-dihydro-2H-l,4-benzodiazepin-2-one as pale yellow crystals.

Melting point: 212 to 213 C.

' EXAMPLE 3 EXAMPLE 4 A solution of 1.28 parts of 2-hydroxy-7-nitro-S-phenyl-2,3-dihydrol H- l ,4-benzodiazepine hydrochloride prepared in the Example 3 in 8 parts by volume of pyridine is added dropwise with stirring and ice-cooling to a mixture of 0.8 part of chromium trioxide in parts by volume of pyridine.

The mixture is left standing at room temperature for 2 hours and poured into water, followed by extraction with ethyl acetate. The ethyl acetate layer is washed with water and dried over sodium sulfate, followed by distillation of the solvent. The residue is crystallized from ethanol to yield 7-nitro-5-phenyl-1,3-dihydro-2H- l,4-benzodiazepin-2-one as pale yellow plates. Melting point: 223 to 224 C.

EXAMPLE 5 To a mixture of 3.2 parts of 2-hydroxy-7-nitro-5- phenyl-2,3-dihydrol H- l ,4-benzodiazepine hydrochloride and 50 parts by volume of glacial acetic acid is addeddropwise with stirring a mixture of 1.5 parts of chromium trioxide, 30 parts by volume of glacial acetic acid and a small portion of water. The mixture is left standing for 2 hours. The solution is poured into water and neutralized with sodium bicarbonate, followed by extraction with ethyl acetate. The ethyl acetate layer is washed with water and dried over sodium sulfate, followed by distillation of the solvent. The residue is recrystallized from ethanol to yield 7-nitro-5- phenyl-l,3wdihydro-2H-1,4-benzodiazepin-2-one as yellow crystals.

Melting point: 220 to 222.5 C.

EXAMPLE 6 A solution of 3.6 parts of 5-chloro-2-inethylamirio-aphenylbenzylideneaminoacetaldehyde diethylacetal in 30 parts by volume of ethanol containing 10 percent hydrogen chloride is left standing at room temperature overnight, followed by concentration to dryness at room temperature under reduced pressure. The yellow residue is dissolved in 50 parts by volume of glacial acetic acid and to the solution is gradually added a mixture of 3 parts of chromium trioxide, 10 parts by volume of glacial acetic acid and a small portion of water. The whole mixture is left standing for 1 hour, followed by addition of water. The mixture is extracted with ethyl acetate. The ethyl acetate layer is washed with water, dried over sodium sulfate, followed by distillation of the solvent. The residue is recrystallized from an acetone-petroleum ether mixture to give 7- chloro-l-methyl-5-phenyl-l ,3-dihydro-2H- l ,4- benzodiazepin-2-one as colorless crystals.

Melting point: 1 30 to 132 C.

EXAMPLE 7 A solution of 3.6 parts of 5-chloro-2-methylamino-aphenylbenzylideneaminoacetaldehyde diethylacetal in 30 parts by volume of ethanol containing 10 percent hydrogen chloride is left standing at room temperature for 20 hours, followed by distillation of the solvent below 25 C. under reduced pressure. The precipitated crystals are treated with a small amount of aqueous acetone to yield 7-chloro-2-hydroxy-l-methyl-5-phenyl-2,3-dihydrol H- l ,4-benzodiazepine hydrochloride as yellow crystals.

Melting point: 108 to 1 10 C. (decomposition).

Elementary analysis:

Calculated for C H ClN 0'HCl-2/3H 0 C 57.32, H

Found C 57.24, H 5.19, N 8.00

What is claim is:

1. A process for producing a compound of the formula wherein R is hydrogen or lower alkyl and the rings A and B are unsubstituted or substituted by at least one of the substituents selected from the group consisting of nitro, trifluoromethyl, halogen, lower alkyl and lower alkoxy groups, which comprises contacting a compound of the formula wherein R, is as defined above, R, is lower alkyl and the rings A and B are unsubstituted or substituted as defined above, with an acid in the presence of a nonaqueous solvent at a temperature from room temperature to the boiling point of the solvent to effect ringclosure, hydrolyzing the resultant product with water to prepare a compound of the formula 

2. The process as claimed in claim 1, wherein the oxidation is carried out by means of chromium trioxide as an oxidizing agent. 